|
Road diets in the Seattle
area, the daily load before and after the diet and the dropin
number of accidents.
|
Roadway
|
Date
of Change
|
ADT
Before
|
ADT
After
|
Collisions
|
|
Greenwood
Ave.
|
April
1995
|
11872
|
12427
|
58%
fewer
|
|
45th
Street
|
December
1972
|
19421
|
20274
|
49%
fewer
|
|
8th
Ave.
|
January
1994
|
10549
|
11858
|
61%
fewer
|
|
MLK
drive
|
January
1994
|
12336
|
13161
|
60%
fewer
|
|
Dexter
Ave
|
June
1991
|
13606
|
14949
|
59%
fewer
|
|
24th
Ave
|
October
1995
|
9727
|
9754
|
28%
fewer
|
From Road Diets:
Fixing the Big Roads
by Dan Burden and Peter Lagerwey
- A study published
in 2002 (Huang, Stewart, Zegeer, 2002) reported that in Oakland
CA, a street carrying 24,000 trips per day was converted from
four lanes to three. The number of annual crashes went from 81
before to 68 after.
- When another street
in Oakland was put on a road diet, crashes went down 52 percent.
- In Minnesota, a road
diet resulted in a 33-percent reduction in injury crashes.
- In Lewistown PA, removal
of travel lanes saw the number of crashes drop to almost zero.
- In Seattle WA, a number
of road diets were analyzed, and a 34-percent
- reduction in total
crashes and a 7-percent drop in injury crashes was noted.
- The Iowa Department
of Transportation (2001) has found that converting a four-lane
undivided road to three lanes can improve safety while retaining
an acceptable level of service. Their review of research found
that when such conversions occurred, there was a significant reduction
in speeding, and a substantial reduction in the total number of
crashes.
- Welch reports that
in Billings MT, when a four-lane was converted to a three-lane
road, the number of reported accidents decreased from 37 in the
20 months before to 14 in the 20 months after conversion. No increase
in traffic delay was found.
- Despite initial apprehension
from the local community and its engineers, Welch indicates that
a conversion from four lanes to three in Storm Lake IA (US 71)
resulted in an observed improvement in safety ("an immediate
large reduction in accidents"). The Iowa DOT Office of Transportation
Safety has begun actively promoting conversion of four-lane roads
to three-lane when a concern about safety is expressed.
- In Helena MT, an urban
primary highway (US 12) was converted from four lanes to three.
(City staff and other state staff engineers now support the conversion
after observing an improvement in traffic operations and a reduction
in accidents.)
- In a study conducted
for the Minnesota DOT, it was found that the highest urban corridor
accident rates are found on four-lane undivided roads. In fact,
the collision rate was 35 percent higher than on urban three-lane
roads. Howard Preston, who conducted the study, stated that he
would convert most four-lane roads with less than 20,000 car trips
per day to three-lane roads "in a heartbeat."
- In Duluth MN, a conversion
from four lanes to three (21st Ave East) was initially opposed
by many. After conversion, the Duluth News-Tribune editorial had
this to say: "When Duluth officials announced they would
convert busy 21st Avenue East...from four lanes to two, with a
turn lane in the middle, some armchair analysts predicted it wouldn't
work. The News-Tribune Opinion page was among them. Well, it works.
About everyone agrees-from city traffic officials to neighbors-that
the change has eased congestion and reduced drivers' speed making
it safer for pedestrians..."
From Bigger Roads
are Less Safe
by Don Nozzi
|
